Factories, office buildings, educational institutions and the like typically employ monitoring systems for surveillance and security purposes. Such systems are typically comprised of a closed circuit television network having a plurality of television cameras each arranged to view a particular location. In order to avoid the complexity and cost of providing one TV monitor per TV camera, switchers have been employed to affect the switching of a single TV monitor sequentially from one TV camera to the next, so that an observer need only look at a single TV monitor, which monitor is connected in sequence to each of the TV cameras. Whenever it is unnecessary to observe one or more particular locations being monitored by associated TV cameras, a selector switch on the switcher apparatus allows said location or locations to be "skipped". Likewise, the monitor may also be "held" so that the region being observed by that camera is constantly displayed on the monitor until it is desired to advance to the next observation location.
Conventional switchers have employed discrete rather than integrated semiconductor devices. The circuitry employed for skipping or holding a TV camera has involved rather tedious and complex construction techniques requiring at least one switch per TV camera position, thus, significantly adding to construction costs and maintenance requirements due to the fact that deterioration of switch contacts has become a troublesome aspect of the system.
In addition to the above, present day switchers have been found to have other design limitations. For example, the devices employed for electronic switching in conventional apparatus have made the switcher a "passive" part of the video circuit, causing the TV camera signals to be attenuated by the switcher, rendering it difficult, if not impossible, to drive more than one monitor even though the ability to monitor one TV camera in a plurality of different locations is a most desirable feature. As a result, it became necessary to provide separate amplifying devices for each such location. In addition to the above, since all of the controls such as the "hold" and the "skip" controls of the switcher are arranged on the switcher itself, the TV monitor which is located remote from the switcher is only of limited use since the person observing the remote monitor does not have the ability to operate the switcher to the "hold" condition should he desire to "hold" one particular TV camera. Thus present day systems would be more versatile if each remote monitor were provided with a "hold" switch allowing a selection of a particular TV camera from any monitor in the system.
Conventional switchers have the further limitation of requiring a lighted indicator at each switcher position making observation inconvenient, if not difficult, in low light conditions, since the non-illuminated designating numeral for the particular camera switched into the circuit is not readily apparent, requiring that ambient light be significantly increased in order to be able to observe the camera designation number next to the lighted indicator. These disadvantages lead to a rather tedious and complex switcher assembly.